1. Field of the Invention
The invention relates to a sealing device and a rolling bearing unit, and more specifically to a sealing device suitable for a rolling bearing unit that is used in an environment in which water is likely to enter the rolling bearing unit from the outside, such as a bearing unit for a wheel of a vehicle and a rolling bearing unit including such a sealing device.
2. Description of Related Art
In a rolling bearing unit used in a hub unit for a vehicle, a sealing device called a pack seal is commonly used. Such a sealing device usually includes a first metal core having a generally L-shaped cross section, an elastic seal, and a second metal core (slinger) having a generally L-shaped cross section. The first metal core has a cylindrical portion that is fitted to an outer ring. The elastic seal is attached to the first metal core. The second metal core has a cylindrical portion that is fitted to an inner ring. The elastic seal is in sliding contact with the second metal core, and a small clearance (clearance for a labyrinth seal) is formed between the cylindrical portion of the first metal core and an outer peripheral edge of the second metal core.
Due to presence of the clearance between the cylindrical portion of the first metal core and the outer peripheral edge of the second metal core (due to the non-contact type seal configuration), there is a problem that water is likely to enter the rolling bearing unit. In order to address the problem, Japanese Patent Application Publication No. 2005-257015 (JP 2005-257015 A) proposes a sealing device with a configuration in which part of an elastic seal and a sliding ring joined to the part of the elastic seal are provided between the cylindrical portion of the first metal core and the outer peripheral edge of the second metal core.
In the sealing device described in JP 2005-257015 A, although the sealing performance is improved by filling the clearance (by realizing contact-type seal configuration), there is a problem that manufacturing and assembly of the sealing device become cumbersome because the sliding ring, which is not used in a conventional sealing device, is required.